Fiber optic gyroscope is an instrument used to measure angular velocity based on Sagnac effect, which is mainly used in inertia measurement systems. Nowadays, the mature and extensively used versions are mainly interferometric digital closed loop fiber optic gyroscopes. The light source is split into two counterpropagating beams of light by a coupler and a multi-functional integrated optic chip. When the sensitive axis direction of the fiber coil has an angular velocity input, Sagnac phase difference is produced between the two beams of light and interference occurs. Then it is transformed into an electronic signal by detector and after processing, the corresponding input angular velocity can be obtained.
Fiber optic gyroscopes have the advantages of small volume, light weight, quickness to startup, high reliability and long-life etc., therefore they are widely used in the systems of navigation, control and so on. Nowadays, the domestic and overseas fiber optic gyroscopes mostly employ a polarization-maintaining fiber coupler as the light source splitter and adopt all-polarization-maintaining scheme in light path, the techniques have been mature and the fiber optic gyroscopes with all-polarization-maintaining scheme have been produced in large quantities in foreign countries. But the all-polarization-maintaining light path scheme has strict requirements of polarization-maintaining property and polarization stability of the light source and the polarization-maintaining fiber coupler and has tendency to be affected by outside environmental factors. In addition, the all-polarization-maintaining scheme has strict requirements of assembling techniques and axis-aligning accuracy, and the cost of the light path is high, which is disadvantageous for manufacture in large quantities. Furthermore, since the domestic manufacture technique for polarization-maintaining fiber couplers is not mature enough, it is necessary to research the fiber optic gyroscope of non-all-polarization-maintaining light path based on single mode optical coupler and try to achieve implementation in engineering and large scale production as soon as possible, so as to meet the requirements of our country for fiber optic gyroscopes in the systems such as navigation and control.